InGaN/Si Double-Junction Photocathode for Unassisted Solar Water Splitting
Srinivas Vanka, Baowen Zhou, Rasha A. Awni, Zhaoning Song, Faqrul A. Chowdhury, Xuedong Liu, Hamed Hajibabaei, Wen Shi, Yixin Xiao, Ishtiaque Ahmed Navid, Ayush Pandey, Rong Chen, Gianluigi A. Botton, Thomas W. Hamann, Dunwei Wang, Yanfa Yan, Zetian Mi
Abstract
Simultaneously achieving efficient and stable operation is a major challenge for developing sustainable and economical solar water-splitting systems. In this work, we demonstrate, for the first time, a monolithically integrated InGaN/Si double-junction photocathode, which can enable relatively efficient and stable unassisted solar water splitting. The device consists of a p-type InGaN top junction, which is monolithically integrated on a bottom Si p–n junction through a dislocation-free n++/p++ InGaN nanowire tunnel junction. With the incorporation of Pt catalysts and a thin Al2O3 surface passivation layer, a solar-to-hydrogen efficiency of ∼10.3% and stable operation of 100 h was measured in 0.5 M H2SO4 in a two-electrode configuration for unbiased photoelectrochemical water splitting. Significantly, such an efficient and stable water-splitting device is achieved using the two most produced semiconductors, i.e., Si and Ga(In)N, promising large-scale implementation of efficient, stable, and low-cost solar hydrogen production systems.